What happens if you add tap water to a car?

[DeWalker]

Adding tap water to a car can have the following effects: 1. The engine and its cooling system are made of metal, including copper, iron, aluminum, steel, and solder. These metals, when exposed to water under high temperatures over time, can corrode and rust. 2. The boiling point of water is 100 degrees Celsius. During summer use, when the engine operates at higher temperatures, adding tap water can easily lead to boiling. 3. The most troublesome issue with using water as a coolant is the problem of scale. Scale deposits on the metal surfaces of the radiator and water jacket, which increasingly reduces cooling efficiency and is difficult to remove.

[LaJude]

After driving for so many years, I've seen plenty of car owners trying to save money by adding tap water to their cooling systems, only to suffer major consequences. The calcium and magnesium ions in tap water form scale deposits in the radiator pipes when exposed to high temperatures, just like the white buildup at the bottom of an electric kettle. Over time, this scale accumulates and completely blocks the cooling channels. Once, a friend's car suddenly started spewing white smoke while driving, and when towed to the repair shop, they found the entire cooling system clogged with scale—costing over 5,000 yuan in repairs. In summer, poor cooling can cause engine cylinder scoring, and in winter, water freezing below zero degrees expands, cracking the radiator outright. Tap water is even worse for windshield washer fluid—it fails to clean oily dirt properly in the rain, and within six months, the nozzles get clogged with scale. It’s far more practical to spend a few dozen yuan on dedicated coolant, which won’t fail for five years.

[AlanMarie]

Last year, for convenience, I added tap water to my car instead of coolant, and problems arose within less than three months. After starting the vehicle, the temperature gauge skyrocketed to the red line, forcing me to pull over and shut off the engine. When towed to the repair shop for inspection, it was found that the aluminum pipes in the radiator were corroded and perforated by the tap water, with leaks also occurring at the hose connections. The mechanic explained that tap water contains chlorine and salts, which act like a slow poison, corroding metal parts over time. To make matters worse, adding tap water to the washer fluid reservoir caused it to freeze in winter, burning out the windshield washer pump. Later, I spent two thousand yuan to replace the damaged parts and had to repeatedly flush the entire cooling system. Now, I only use green antifreeze coolant, which prevents corrosion and has a high boiling point, allowing me to drive even in temperatures as low as minus twenty degrees Celsius in winter.

[AugustLynn]

The biggest headache of using tap water is the scale problem. I once saw a car's cylinder head removed, and the water passages were clogged like a stalactite cave. These scales affect the cooling efficiency, causing the engine to run at high temperatures continuously. Even worse, tap water freezes and expands below zero degrees, potentially cracking the cast iron engine block. As for windshield washer fluid, tap water can't effectively clean bird droppings or tree sap, leaving water stains all over the windshield after sun exposure. In emergencies, bottled purified water is the maximum you should use, and it must be replaced after driving 300 kilometers.